[Problem] To improve productivity and reduce price of mesh filters while maintaining filter performance. [Solution] A filter section (4) that connects a gate-connecting section (2) with an outer tube (3) comprises, when an imaginary plane that is orthogonal to the central axis (5) of the gate-connecting section (2) is called the X-Y plane: multiple longitudinal ribs formed to be orthogonal to the X-axis and parallel to the Y-axis at equal intervals; multiple transverse ribs formed to be orthogonal to said longitudinal ribs and parallel to the X-axis at equal intervals; and multiple square openings formed between said longitudinal ribs and transverse ribs. By injection of melted resin into the cavity section for forming the gate-connecting section (2) from a gate that opens into the cavity, not only are the gate-connecting section (2), outer tube (3) and filter section (4) integrally formed but also the longitudinal ribs and transverse ribs are formed with fixed rib widths and the multiple openings are formed with the same shape.